[Disorders of motor unit discharge activity in parkinsonism]

The discharge activity of single motor units (MUs) of the first dorsal interosseus muscle was recorded in slight stationary isometric contractions. Normal subjects and patients with parkinsonism of various degrees were investigated. The purpose was to study disturbances of the discharge pattern in the patients and their potential diagnostic role. Automatic signal recognition and statistical analysis of the interval distribution were used. Most MUs of the patients revealed considerable irregularities of their discharge sequences best marked by the so called "floating standard deviation". All patients, also 2 without tremor, showed a characteristic synchronization of their MU discharges ("broad-peak" type). Since the above changes were also seen in the patients with only slight symptoms, these investigations, if methodically simplified, could be of diagnostic value.